1. Field of the Invention
The present invention relates to a disc cartridge having spinnably encased therein a disc-shaped recording medium such as an optical disc, magneto-optical disc or the like (will be referred to as "disc" hereinunder) to which information signal such as audio signal, video signal or the like can be written or from which recorded information signal can be read.
2. Description of Related Art
FIG. 1 shows a conventional disc cartridge by way of example. The disc cartridge is generally indicated with a reference 101. It has encased therein a disc 105 to which information signal such as an audio, video signal, etc. can be written or from which recorded information signal can be read. As shown, the disc cartridge 101 has a cartridge body 104 formed from a combination of an upper half 102 and a lower half 103. The disc 105 is housed spinnably in a disc compartment formed inside the cartridge body 104. When the disc cartridge 101 is set in a recording/reproducing apparatus (will be referred to as "disc drive" hereinunder), the disc 105 is connected to a disc table of a disc spinning drive and driven to spin.
The cartridge body 104 has read/write openings 106 formed therein. At least portions thereof extending from the lead-in to lead-out of an information recording area of the disc 105 housed spinnably in the disc compartment, are exposed through the read/write openings 106. There is provided on the cartridge body 104 a shutter member 107 which is movable between two positions, open and closed. When the disc cartridge 101 is not used, the shutter member 107 is in the closed position to prevent dust or the like from coming into the cartridge body 104 through the read/write openings 106 and adhering to the surface of the disc 105 in the cartridge 101. When the disc cartridge 101 is used for read or write with respect to the disc 105, the shutter member 107 is moved to the open position. The cartridge body 104 has formed on one side face 104a thereof (will be referred to as "front face" hereinunder) a guide recess 104b in which a shutter opening member 109a of the disc drive is engaged as will be described later.
The shutter member 107 is formed from a thin metallic material such as a stainless steel by punching, bending or cutting. As shown in FIG. 2, the shutter member 107 consists of shutter portions 107a and 107b parallel to each other and corresponding to the read/write openings 106, respectively, formed in the upper and lower halves 102 and 103, and a joint portion 107c. Thus the shutter member 107 has a generally C-shaped section. The shutter member 107 has a sliding guide portion 107d formed integrally at one end of the joint portion 107c and which is to guide the shutter member 107 sliding along the front face 104a of the cartridge body 104.
The joint portion 107c has formed therein an engagement hole 107e in which a shutter closing member 109b of the disc drive is engaged. The sliding guide portion 107d has an engagement lug 107f formed at the free end thereof. The engagement lug 107f is bent from the upper edge of the sliding guide portion 107d to be parallel to the shutter portion 107a. A shutter locking member 108 provided on the cartridge body 104 as will be described later is engaged on the engagement lug 107f. The shutter member 107 constructed as mentioned above is assembled from the front face 104a of the cartridge body 104 for the shutter portions 107a and 107b to extend over the read/write openings 106.
As indicated with dashed lines in FIG. 1, the cartridge body 104 has the shutter locking member 108 disposed at one corner 101a of a front face 103a of the lower half 103 forming the front face 104a. The shutter locking member 108 is made of a synthetic resin. While the shutter portions 107a and 107b are closing the read/write openings 106, respectively, the shutter locking member 108 locks the shutter member 107 at the closed position against an inadvertent movement to open the read/write openings 106.
The shutter locking member 108 consists of a fixed portion 108a formed at the base of the member 108 and which is to be fixed to the lower half 103, a locking arm portion 108b formed integrally with the fixed portion 108a to project and have a generally U-shaped form, and an engagement concavity 108c formed at the free end of the locking arm portion 108b. The locking arm portion 108b is elastically deflectable. The shutter locking member 108 is installed to the lower half 103 for the engagement concavity 108c of the locking arm portion 108b to be opposite to the front face 104a of the cartridge body 104. When the engagement lug 107f of the shutter member 107 is engaged in the engagement concavity 108c of the locking arm portion 108b with the shutter portions 107a and 107b closing the read/write openings 106, the shutter locking member 108 locks the shutter member 107.
In the conventional disc cartridge 101, when the engagement lug 107f of the shutter member 107 is engaged in the engagement concavity 108c of the locking arm portion 108b with the shutter portions 107a and 107b closing the read/write openings 106, the shutter locking member 108 locks the shutter member 107 as mentioned just above. Even if the disc cartridge 101 is applied with a shock by dropping or otherwise careless handling, the read/write openings 106 can be surely closed by the shutter member 107.
The engagement lug 107f of the shutter member 107 is formed by bending horizontally from the upper end of the sliding guide portion 107d towards the cartridge body 104. Thus, if the shutter member 107 is applied with a shock, the engagement lug 107f will possibly be bent inwardly as shown in FIG. 3 as the case may be. In this case, in the disc cartridge 101, the engagement lug 107f is disengaged from the engagement concavity 108c of the shutter locking member 108 so that the shutter member 107 will easily be moved, with the result that the read/write openings 106 will be opened. Dust or the like coming into the cartridge body 104 through the read/write openings 106 thus opened will adhere to the exposed surfaces of the disc 105 which will also be scratched or otherwise damaged.
On the other hand, it has been proposed to provide a disc cartridge 101 having the shutter member 107 molded from aluminum or synthetic resin in order to reduce the manufacturing costs or reduce the weight of the disc cartridge 101. In this case, however, since the shutter member 107 made of such a material is somewhat lower in mechanical strength than the stainless steel-made shutter member 107, the engagement lug 107f is deformable or breakable more easily.